The present invention relates to a modified asphalt filler and sealant composition that is useful for repairing joints or cracks in concrete and asphalt surfaces. More specifically, this invention relates to an asphalt-rubber emulsion useful as a filler and sealant material that can be applied to concrete or asphalt at ambient temperatures.
Modified asphalt filler and sealant materials are commonly utilized to repair cracks, joints and other crevices in concrete and asphalt surfaces. To prevent roadway deterioration caused by water intrusion at concrete slab junctures for example, or through an asphalt surface crack, the filler material must completely seal the crack. In addition, the filler material should provide a seal that is not susceptible to deterioration caused either by traffic stress, or by the contraction and expansion of surrounding concrete during freeze thaw cycles. Therefore the filler material must exhibit elasticity, flexibility, good adhesion to the walls of a joint, and overall resistance to cracking and failure.
In order to obtain a sealant having these desired physical properties, it is known to add rubber or other elastomer modifiers to asphalt. In the past, these asphalt-rubber sealants have been applied while hot so that the sealant material is fluid. This permits easy pour application such that the void is completely filled and adhesion to the joint walls is enhanced. Although these "hot pour" sealants have utility, there are some problems associated with their use. One such problem is the necessity to have heating equipment, namely, oil jacketed double boilers, at the work site. This bulky equipment has to be transported to the site by special vehicles and must be cleaned, along with the applying apparatus, at the end of each work day. Another practical problem associated with the use of combustion heaters and hot asphalt materials is the risk of fire and accidental burn injuries. Aside from these more or less irritating and cumbersome problems, the effectiveness of the sealant material can be reduced by thermal degradation which accompanies high temperature maintenance for relatively long periods of time.
Due to the problems associated with hot pour sealants, proposals have been made to provide a filler and sealant material comprising a water-based emulsion of asphalt and rubber that can be applied cold. In general, the asphalt and rubber components are first blended and can be reacted with a cross-linking agent to provide an elastic and uniform asphalt-rubber base composition. This composition is then emulsified with an aqueous medium to provide the cold pour emulsion. By providing the asphalt-rubber components in an emulsion form, they can be applied cold. Following application, the aqueous component of the emulsion evaporates and the resulting dry emulsion residue remains as a filler and sealant. Although asphalt-rubber emulsions represent a potential alternative to the hot pour sealants previously utilized, it has proven difficult to successfully obtain emulsions that exhibit the properties necessary to compete as a viable alternative.
One such difficulty relates to the amount of water present in the emulsion, and correspondingly, to the solids content of the emulsion. A certain minimum amount of water is needed to provide a uniform emulsion that is fluid enough for cold pour applications. However, an emulsion having a relatively high water content takes longer to dry and therefore delays use of the repaired roadway following application. Furthermore, an aqueous emulsion having a relatively low asphalt rubber solids content and a correspondingly high aqueous content will shrink upon evaporation of the water content. This shrinkage results in a failure to adequately fill and seal the repaired crack or joint. Therefore, it is desirable to provide an emulsion comprising a minimum amount of water to permit cold pour application and a relatively high solids content so that upon application, the sealant will dry quickly and without significant shrinkage.
In order to provide a uniformly blended emulsion having a relatively high solids content, it is known to utilize an asphalt-rubber base composition for emulsification that has a relatively low viscosity. These less viscous compositions tend to be more easily emulsified and provide an emulsion with a suitable viscosity for cold pour application. However, even though the emulsifiability of the solids is enhanced by using less viscous asphalt-rubber blends, other desirable properties of the emulsion residue, such as good elasticity, may be diminished by their use. For example, an asphalt-rubber composition that is highly cross-linked tends to exhibit a relatively high viscosity. Therefore, even though it is desirable to cross-link the asphalt-rubber components of the emulsion to provide a uniformly elastic residue, excessive cross-linkage is avoided so that a less viscous composition is provided for emulsification. In the past, this has been accomplished by cross-linking the asphalt-rubber compositions via slow reactions that last for a relatively long period of time, such as those utilizing styrene monomers for example, and that result in a loosely cross-linked asphalt-rubber blend having the requisite viscosity. Another factor that can effect the viscosity of an asphalt-rubber composition is the amount of rubber present in the composition. Thus, it is also known to prepare asphalt-rubber compositions for emulsification that have a relatively small amount of rubber and correspondingly lower viscosity.
Although some of the emulsion compositions heretofore provided have been prepared in a manner to enhance the emulsification of a relatively high amount of asphalt-rubber solids, the resulting emulsion residue often lacks other desirable properties such as enhanced elasticity, viscosity and resilience. Notably, a reduction in cross-linkage or in rubber content reduces the elasticity of the sealant material. In addition, the styrene monomers commonly utilized in slow cross-linking reactions tends to polymerize to form a hard polystyrene component in the composition. The presence of this polystyrene component reduces stress relaxation, elasticity and the overall bonding properties of the emulsion residue. Furthermore, the emulsion residues made in the past having a relatively low viscosity for emulsification purpose generally also have a relatively low softening point. During summer months at temperatures above about 90.degree. F., for example, the asphalt roadway surfaces become very hot and these residues may require dusting for traffic use. In short, reduced viscosity, cross-linking, and rubber content for practical processing purposes is not necessarily desired for operational purposes. Although the emulsion needs to have a relatively low viscosity to permit pouring application at ambient temperatures, it is preferable to provide an emulsion residue that is highly cross-linked, having a relatively high amount of rubber such that it exhibits superior elasticity, and having a relatively high viscosity.
Many of the important properties that determine the overall effectiveness of a sealant material such as the ability of good adherence and bonding at high and low temperatures, good elasticity such that the seal lasts for a long time without deterioration, and a high solids content to prevent shrinkage and prolonged drying times have heretofore been lacking in the art. In summary, an emulsified cold pour sealant that is equal to or superior to known hot pour sealants in overall performance is lacking in the art.
It is there an object of the present invention to provide an emulsified sealant having a high solids content wherein the emulsion residue exhibits good elasticity, stress relaxation, bond, and adhesion properties.
Another object of the present invention is to provide an emulsified sealant having a high solids content that has a relatively low viscosity to permit application at ambient temperatures.
It is another object of the present invention to provide an emulsified sealant having a high solids content wherein the emulsion residue has a relatively high rubber content.
A further object of the present invention is to provide an emulsified sealant having a high solids content wherein the asphalt and elastomer components of the emulsion are reacted to form a highly cross-linked asphalt-elastomer matrix.
Still another object of the present invention is to provide an emulsified sealant having a high solids content wherein the asphalt and elastomer components of the emulsion are reacted in the presence of a peroxide cross-linking agent.
A further object of the present invention is to provide an emulsified sealant having a high solids content wherein the asphalt-rubber base has a relatively high viscosity prior to emulsification.
It is another object of the present invention to provide an emulsified sealant having a high solids content wherein the emulsion residue has a relatively high softening point so that roadway dusting is not required during summer months.
A further object of the present invention is to provide an emulsified sealant having a high solids content which dries relatively quickly upon application so that the repaired roadway can be opened for traffic or other use within a short period of time following application.
A further object of the present invention is to provide an emulsified sealant having a high solids content wherein the emulsion residue does not shrink following application.
It is another object of the present invention to provide an emulsified sealant having a high solids content that meets the requirements of ASTM D 3405 which is directed to hot pour joint sealants for concrete and asphalt pavements.
Another object of the present invention is to provide an emulsified sealant having a high solids content that effectively fills and seals cracks or joints in concrete or asphalt surfaces such that the emulsion residue does not deteriorate over time.
It is another object of the present invention to provide an emulsified sealant having a high solids content for application to a crack or joint in concrete or asphalt surfaces, wherein the emulsion residue exhibits superior bond and adhesion to the walls of the joint even at relatively low temperatures.
A further object of the present invention is to provide an emulsified sealant having a high solids content wherein the emulsion is substantially solvent free to avoid volatile organic chemical evaporation, and to avoid unpleasant odors and health risks to the applicator.
Another object of the present invention is to provide a method for producing an emulsified sealant having a high solids content meeting all of the objectives heretofore mentioned that requires a relatively short production time, thereby providing a more efficient and economical sealant material.
These and other objects of the present invention are achieved by a stable aqueous emulsion comprising a polymeric surfactant and the reaction product of an asphalt-elastomer mixture, a liquid polybutadiene, and a cross-linking peroxide agent wherein the reaction occurs at elevated temperatures for a relatively short period of time. In a preferred embodiment, the emulsion may additionally include an oil modified paraffin wax, a zircoaluminate coupling agent and a vinyl acetate latex thereby providing an emulsion for use as a joint sealant that meets the requirements of ASTM D 3405. The present invention is also directed to a process for preparing the composition wherein an emulsion having a relatively high solids content, preferably ranging from 70 to 85% solids and most preferably from 73 to 80% solids, is prepared. The emulsion residue has a relatively high elastomer content, preferably at least about 8% by weight of the residue is elastomer.
The emulsion of the present invention has good stress relaxation properties which enable the residue to pass stringent low temperature bond tests. The emulsion has good low and high temperature cohesive and adhesive properties such that the seal will not deteriorate upon expansion or contraction of the underlying concrete. The emulsion residue exhibits good adherence to the sidewalls of the crack or joint and exhibits good elasticity such that the material is very rubbery and not brittle.
The composition can be used as a concrete or asphalt crack sealer, joint sealer, filler, an overlay sealant for construction materials and the like .